Let's look at one of HCB's most famous photos, the guy jumping over a puddle, below.
This shot represents recurring symmetries all over the place. It was a stroke of luck. Aparently, the shot was taken through a gap in a fence. HCB didn't even have time to look through the viewfinder. Just pointed the camera and pressed the shutter at the right moment. It was one of the few photos he cropped, apparently because of some vignetting caused by the fence posts.
I'm reminded here of one of Ansel Adams' most celebrated shot, 'Moonrise over Hernandez', which wasn't planned at all, Howard, as you well know.
In photography, sometimes we have the opportunity to plan and sometimes we don't. I think it would be a reasonable case to make that, those occasions when we didn't have the opportunity to plan, post cropping is more common. When we have the opportunity to plan, post cropping might be seen as an indication of incompetence.
It might be the case that users of miniature cameras such as 35mm, are more obsessed with resolution and therefore try harder to maximise their real estate; to search for compositions that fit the aspect ratio, to avoid cropping. I'm certainly aware of such internal pressures. I have been for a long time.
When I bought a 5400 dpi scanner for 35mm, some time ago, and began scanning a bunch of Kodachrome slides I'd taken 40 years ago, for the third time, which were still only slightly faded, I had a sort of epiphany. Why should I be so concerned about extracting the maximum detail from these slides when the Kodak cardbord frame was obscuring up to 1.5mm on each side. There were a few shots where I appeared to have sliced off someone's fingers or toes. Trying to reflect on my level of awareness 40 years ago, and I don't believe I would have done this. I ripped off all the cardboard Kodak frames and discovered I was right. I had in fact carefully framed each shot to maximise the real estate; and that was with just 2 lenses, a standard 50mm and a telephoto 135mm.
I tried to buy some slide frames that are 24mmx36mm, but did not succeed. The best I could do was get some plastic frames that obscured about 1mm on each side. I used a Stanley knife to pare off that obtrusive 1mm and reframed all the slides I wanted to scan.
Jack Flesher's point about his most successful photos not being cropped, rings a bell here. I know Jack is rather obsessed with resolution, as I am. Anyone who is obsessed with resolution does not want to post crop if it can be avoided.
Clearly, there are unavoidable circumstances where cropping is necessary.
(1) You don't have a sufficiently long lens.
(2) You don't have time to stuff around like a gentleman.
(3) You are in an unplanned situation where it's the moment that is paramount.
(4) The subject simply doesn't lend itself to the aspect ratio of your camera, the most basic example of which would be the passport photo in relation to 35mm.